His fellow players have played down reports that the forward won't be functioning for the tournament but as he sat out the Greece friendly there are concerns.

Manager Paulo Bento is rightfully cautious; although he is also optimistic the forward will be fit in time.

He told a press conference before the goalless game at the weekend, via The Daily Mirror:

What I don't want to do is put any sort of pressure on a player that causes them to compete when they are not in the right state to do so. We're not setting any deadlines. The player's well-being comes first. I want him to be in the best possible form without running any risks.

It's natural for a country to build their side around one of the top three players in the world.

In fact, it's natural to build a team around your best player in general.

Although if your nation has other quality players, then it's a little worrying if you play in a one-dimensional manner.

Club sides also face similar dilemmas, but if you have the right sized cheque book that can often be altered.

At Real Madrid, Gareth Bale was purchased to ease the burden on Ronaldo.

When Ronaldo was missing, like in the Copa del Rey final, the Welshman was able to offer similar attributes to the Portuguese superstar.

With both wingers on the pitch, Carlo Ancelotti found a 4-4-2 variation which saw Bale out wide on the right and Ronaldo almost as a second striker starting from the inside left position.

The balance of the team was maintained by Angel Di Maria who could make it three in the centre or move out to track the opposition full-back on the left.

When Ronaldo moved inside it opened up space for Di Maria to exploit and attack.

Portugal don't have any players with characteristics like Ronaldo, perhaps the closest is Manchester United's Nani when at his very best.

Nani is very much out of sorts and therefore Bento can't simply plan to replace Ronaldo like for like.

Without Ronaldo, Portugal's plan B appears to rely on crosses into the box for the physical strikers.

Joao Moutinho's form has been anything but convincing for Monaco this season, though he does offer the side the best chance of creativity without Ronaldo.

Bento does have the options to restructure the team to attack through the middle, but this is something the former Sporting Club coach should have rectified earlier.

"The presence of Ronaldo is good because it frees the attention of the press from the other players, and he is already used to it," said Benfica midfielder Ruben Amorim to a news conference, via ESPN.

Amorim was talking about the pressure around the training camp, but he could easily have been speaking about on the pitch.

Ronaldo is crucial to his country's progression in the tournament, but there's a balancing act to be maintained in the coming weeks.

Bento needs to use Ronaldo cleverly throughout the opening stages, whilst simultaneously ensuring Portugal negotiate their way out of a tricky group.